Question

Which of the following is not a statement?
(A) Multiple bonds are always shorter than corresponding single bonds.
(B) The electron-deficient molecules can act as Lewis acids.
(C) The canonical structures have no real existence.
(D) Every $ \text{A}{{\text{B}}_{\text{5}}} $ molecule does in fact have a square pyramid structure.

Answer 1

Hint: A chemist specifies the molecular geometry and, where feasible and essential, the electronic structure of the target molecule or other solid during a chemical structure determination. The spatial arrangement of atoms in a molecule, as well as the chemical bonds that keep them together, may be expressed using structural formulas and molecular models; full electronic structure descriptions also involve describing the occupation of a molecule's molecular orbitals.

Complete Step By Step Answer:
Multiple bonds are always shorter than single bonds of the same length. Lewis acids can be formed by electron-deficient compounds. The canonical structures do not exist in reality. A double bond is a covalent connection between two atoms that involves four bonding electrons rather than two in a single bond in chemistry.
Hence it is correct
Lewis acids are electron-deficient compounds (those with less than an octet of electrons). Because it accepts a lone pair of electrons on the base to create a connection, the proton ( $ {{\text{H}}^{\text{+}}} $ ), which has no valence electrons, is a Lewis acid. An electron pair is accepted by Lewis acids. An incomplete octet of electrons in an atom, ion, or molecule can behave as a Lewis acid. Lewis acids are molecules in which the core atom has more than 8 valence shell electrons and so can act as electron acceptors.
Hence it is correct
The canonical forms do not exist in reality. The molecule lives in one canonical form for a specific amount of time and in other canonical forms for other amounts of time. Tautomerism is the fact that there is no such equilibrium between canonical forms as there is between tautomeric forms (keto and enol).
Hence it is correct.
There are three potential geometries for $ \text{A}{{\text{B}}_{\text{5}}} $ molecules: planar pentagonal, square pyramidal, and trigonal bipyramidal. Only the trigonal pyramidal shape has the lowest bond pair-bond pair repulsions of the three geometries, making it the most likely geometry for the $ \text{A}{{\text{B}}_{\text{5}}} $ molecule.
Hence it is incorrect.
Hence option D is correct.

Note:
A trigonal bipyramid formation is a molecular geometry that has one atom in the centre and five additional atoms in the corners of a triangular bipyramid in chemistry. Because there is no geometrical configuration with five terminal atoms in equivalent locations, the bond angles surrounding the central atom are not similar.